Spring



May 9, 1939. `.1. P. BURKE SPRING Filed July 12, 1957 INVENTQR.

@Olli/g) ATTORNEY.

'Patented May 9, 1939 UNITED STATES PATENT OFFICE SPRllNG James P. Burke, Knoxville, Tenn.

Application July 12, 1937, Serial No. 153,206

11 Claims. (Cl. 267-33) 'I'his invention relates lto springs of the type erably surface-bonded to the spiralkl throughout suitable for a variety of uses such as for vehicle the entire length of both surfaces which contact suspensions, power plant suspensions, flexible couthe spiral.

. plings and the like and has for its object to pro- Surrounding the spring l, 2 is a cylindrical cas- 5 vide a spring composed of metal and an elastic ing of greater diameter than the spring when 5 material so combined as to give advantageous the spring is in normally unloaded position, as springing characteristics of each type of material illustrated. The casing 5 is-bolted or otherwise and so arranged as to be capable of adaptation secured to a'n end plate 6 which is intended to to any reasonable predetermined load deiiection be xedly secured to a support 1. One end of the curve. n spiral l is anchored, as indicated at 8, to the end 10 Another object is to provide a spring which plate 6. An end plate 9 is bolted or otherwise is stable against tilting of its axis and flexible secured to the other end of the casing 5 and this to a predetermined degree in a direction circumplate may be attached, if desired, to the support scribing its axis. l 'l although, for many uses it may be left unsup- More particularly it is an object of the inven- .ported according to the illustration. 'I'he plates 15 tion to provide a spring Comprising a metallic e and e each have bearing portions lu axially ofv spiral or volute with the coils thereof separated the casing 5 for the reception of a relatively rotatby elastic material preferably Sllrfeee bended able shaft ll which is attached to the other end thereto, the volume of elastic material varying of the spiral l by means of a plate I2 to which to permit of a Varying spring rate. it is keyed at i3, the spiral being anchored to this 20 Another object is to provide a spring composed plate at i4. An arm l5 serves as a lever by which of inter-leid spirals or volutes of rubber and the shaft il may be rotated to load and unload metal adapted to operate in a direction of rotathe Spring, v tion about the spring axis to store energy therein, In operation, if the shaft Il is rotated away the rubber being subjected largely to torsional from the reader the turns of the spiral l jointly 25 stresses, in combination with a stop means against with the rubber 2 will increase in diameter. If which the metallic member DrOgleSSiVely CellleCtS the metal of the spiral is of uniform cross-secwherebv the maximum stresses to which any part tional area and tensile strength and if the rubber of the spring can be subjected are pre-determined has a uniform modulus of elasticity that part of 3@ and whereby the load deflection ratio of the the spring containing the least amount of metal 30 Spring may be made t0 increase With increasing and the greatest volume of rubber will expand loads in a manner determined by the shape and fastest. Since the anchorage 8 is fixed the part DOSOII 0f the Stop means to rst contact the casing 5 will be in the vicinity Other objects and advantages will hereinafter indicated by the numeral i6. Continued rotation become more apparent es reference is had to the of the shaft i5 will cause continuously and grad- 35 accompanying drawing wherein: ually increasing contact of the periphery of the Fig- 1 iS a longitudinal diametl'ie SeOll spiral, the action being to "unwind the spiral through my improved spring, by bending the metal against its longer cross-sec- Fig. 2 is a transverse diametri@ section teken tional thickness and to impose tension on the 4o along the line 2 2 of Fig. i. rubber in the direction of its length accompanied 4o Fig- 3 iS a View Similar t0 Fg- 1 0f a modled by an amount of transverse shear due to' the fact form 0f the Spring' and that the ycoils expand progressively and not in Fig. 4 is a transversediametrlc section taken .unison The advantage of the xed anchorage 8 along the line 4 4 of Fig' 3 is that the total spring will function under light Fig. 5 is a quarter section of another modification. o

More particularly, l indicates a flat spiral mellllihsirshfoaggt trntgwimsg deflection ratio, becoming very stiff to preclude tual bottoming. v

tween the turns 1s interposed a spiral 2 of elastic ac material such as rubber, the transverse thickness H the arm 51s released S0 thlli'lley Spring 1S of which is slightly less than that of' the metal allowed t0 return i0 normal and the arm l5 then turns so that the metal extends slightly beyond swung toward the reader 'the Spiral tends to the rubber both internally as indicated at 3 and Wind 11D 0r progressively contract, against the 55 externally as indicated at I. The rubber 2 is prefshaft Il, that portion whlch formerly first con- 55 loading, that is, until the spiral begins its contact 45 with the casing, and thereafter as the contact increased the spring will gradually increase its load tacted the casing 8 now being first to contact'the shaft.V

The design is subjectto numerous mcdicatlons to Aaccommodate the spring to a particular use or drical in preferred form may have some other suitable internal shape as for instance that of a frusto cone as indicated by the dotted line I1 and the outside or inside diameter of the turns o'f the spiral need not necessarily be uniform.

In Figures 3 and 4 the spring is illustrated as being of volute shape. The metallic volute I8 is anchored at one end I9 in a load imposing shaft.

20 which is rotatably mounted in bearings 2.I of a casing 22 which is the load receiving member, the other end of the volute I8 beingY anchored to the casing at 23 as by fitting into a groove 24 provided for the purpose. The volute I8 preferably 'varies in width progressively outwardly and between the coils thereof is interposed a continuous layer 25 of elastic material, such as rubber, which is preferably surface-bonded at both contacting surfaces to the adjacent coils. Secured to one or both exposed ends of the shaft 20 is a lever arm 26.

Due to the tapering shape of the volute I8 the outer or edge portions 21 thereof are covered by rubber only on the inside. The inside of the casing 22 is formed at 28 somewhat, but not exactly, in counterpart of the shape of the outside of these exposed portions 21. The casing formations are larger to provide initial clearance.-

' 1n operation, if the arm 26 is rotated away from the reader the volute tends to unwind, the coils increasing in diameter'thereby imposing tension stresses in the rubber 25. Thematter of whether or not all of the surfaces 21 contact the portions 28 throughout their length simultaneously, or whether the contact is progressively inwardly or progressively outwardly depends upon the amount of taper of the metallic volute. In preferred form it is, as illustrated, proportioned to obtain contact progressively outwardly in order to obtain a spring rate or load deection curve of progressively increasing stiffness under increasing loads.v

In Fig.' 5 a spiralled volute 29 of metal is formed with outturned flange portions 30 which are turned downwardly at the Iouter edge 8|. Interposed between the coils of the volute 29 is a layer of elastic material 32 surface bonded on each side to the volute. The flange 30is of sulcient width to span the elastic layer. When aload is imposed axially of the volute the elastic layer is subjected to shear. Due to the fact that the shear areas become progressively smaller toward the inside of the spiral and due to the fact that the stiffness of the spiralv does not, in my design, increase to a lcompensating extent, the innermost turn will deflect faster than the remaining turns. 'I'he uppermost part of the step 3l will therefore contact the iiange 30 therebelow first and the amount of contact will gradually increase with decreasing loads. The load deection ratio vincreases as the amount of spring employed decreases.

Various modifications will suggest themselves to those skilled in the art and I, therefore, desireto be extended protection within the scope of the appended claims.

What I claim is:

1. A spring comprising a wound metal spring having a plurality of turns, elastic material sepa- 'rating said turns, and stop means separated from said spring against which said metal spring contacts progressively and over a continuously increasing length during continuing deflection of the spring.

2. A spring comprising a metallic spiral spring and elastic material between the coils of said spiral spring and surface-bonded thereto, and stop means separated from said spring and against which said spiral spring progressively contacts during continuing deflection of the spring.

3. A spring comprising a metallic spiral spring and elastic material between the coils of said' spiral spring and surface-bonded thereto, and stop means concentric with said spiral spring constituting means for limiting the amount of deflection thereof, said stop means serving also as a housing for said spring.

4. A spring comprising a metallic spiral spring and elastic material between the coils of said spiral spring and surface-bonded thereto. and a cylindrical casing constituting a housing for said spring y and also a stop means for progressively precluding a continuously increasing portion of said spring from further deflection under increasing loading.

5. A spring comprising a metallic spiral spring and elastic material between the coils of said spiral spring and surface-bonded thereto, and a casing about said spring having a frusto-conical internal shape constituting means for progressively precluding a continuously increasing amour@f of said spiral' spring from further deflection under increasing loading. f

6. The combination of a coil spring, a load receiving member to which one end of said spring is anchored, a shaft extending axially of said spring to which the other end of said spring is anchored, a load imposing member which, upon actuation, expands or contracts said spring diametrically, and stop means concentric with the axis of said coil individually limiting the amount of the expansion or contraction of each turn of said coil.

7. The combination of a coil spring made of a metallic ribbon, a strip of elastic material between all adjacent turns of said coil and surface bonded thereto at each side thereof, a housing for said spring to which one end of said spring is anchored, a shaft extending axially of said spring yto which the other end of said spring is anchored,

and means for relatively rotating said shaft and said casing thereby expanding said coil spring into progressive contact with said casing.

8. 'I'he combination of a spring comprising a metallic spiral spring and a strip of elastic material surface bonded thereto, and stop means against which said spiral spring progressively contacts during deflection thereof under loading,

I'said means serving also as a housing for said spring.

9. 'Ihe combination of a spring comprising a volute made of flat metal and having rubber interposed between the coils thereof, the outer edges of said volute comprising a non-planar spiral, and stop means also in the form of a spiral lagainst which said volute progressively contacts during deflection of said spring.

10. 'I'he combination of a spring comprising a metallic volute having cross-sections which gradually decrease in area radially outwardly and a volute of elastic material interposed between the turns of said metallic volute, theV edges of said metallic volute being exposed and constituting oppositely inclined spirals, and a casing for said spring to the encircling wall of which the t outer end of said metallic spiral is anchored, lthe end walls of said casing each having an internal spiral shape, similar to the exposed edges of said metallic spiral, and load imposing means axially of said metallic spiral, said load imposing means upon actuation in one direction unwinding said metallic spiral thereby causing said exposed edges to gradually contact the spiral formations of said casing.

11. The combination of a spring comprising a metallic volute having cross-sections which gradually decrease in area radially outwardly and a volute of elastic material interposed between the turns of said metallic volute. the edges of said metallic volute being exposed and constituting oppositely inclined spirals. and a casing for said 3' spring to the encircling wall oi.' which the outer end oi' said metallic spiral is anchored, the end walls ot said casing each having an internal spiral shape similar to the exposed edges of said metallic spiral, and load imposing means axially of'said metallic spiral, said load imposing means upon actuation in one direction unwinding said metallic spiral thereby causing said exposed edges to gradually contact the spiral formations of said casing, said load imposing means upon actuation in the opposite direction contacting the coils of said metallic volute thereby imposing compression on said elastic material.

JAMES P. BURmI. 

